Joe Staley still not practicing after concussion

Left tackle Joe Staley has not been cleared to practice after he sustained a concussion in the first quarter of Sunday’s 21-19 loss to the Cardinals.

Staley, who observed practice Thursday, took a knee to the head while executing a cut block on the 49ers‘ first offensive play and was slow to get to his feet. Staley said he didn’t sustain the concussion until San Francisco’s second series, when he had a helmet-to-helmet collision with Arizona linebacker Clark Haggans.

Staley said he’s had previous concussions, but “never like that.”

“It was the second one that knocked me out,” Staley said. “The first play, I was fine. I played normal.”

Alex Boone, who replaced Staley against the Cardinals, said he’s ready to make his first career start, if necessary.

“If he’s not ready to go,” Boone said. “I will be.”

Willis still sidelined: Linebacker Patrick Willis (hamstring) was the only other player who didn’t practice Thursday. Willis worked out on an adjacent field with a trainer during the portion of practice open to the media.

Running back Frank Gore was not limited in practice after coach Jim Harbaugh said Monday that Gore was not fully healthy. Gore had just 10 carries in the loss to the Cardinals.

More red-zone work: Harbaugh said the 49ers are placing added emphasis on their red-zone offense this week – working on their red-zone plays during three practice sessions instead of two.

San Francisco ranks last in the NFL in touchdown percentage in the red zone (35.6). The 49ers have scored three touchdowns in their past 19 red-zone trips.

“We’ve got to put points on the board if we want to come away with this one,” tight end Delanie Walker said, looking ahead to Monday night’s game against Pittsburgh. “Red zone will be our biggest key. We get down there a lot, and we don’t get touchdowns. We get a lot of field goals. We need to get touchdowns.”